Mercedes-Benz 320 MOT pass rate & common failures
Across 31 model years and 3,552 tests, the Mercedes-Benz 320 passes its MOT 78.8% of the time. That is 4.3 percentage points better than all cars of a similar age, which fail at 25.5%. Its most common failure areas are lighting & signalling, suspension and brakes.
What the MOT record shows
No single area dominates — lighting & signalling (10.0%) and suspension (9.3%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are headlamp aim, ball joint and rigid brake pipes — headlamp aim alone was recorded 169 times.
Condition tracks the odometer closely. Failures run at 17.1% in the 0-30k band and 22.7% in the 150k+ band, a 5.6-point spread.
Split by fuel, diesel examples fail 5.0pp more often than petrol ones (23.4% vs 18.5%) — worth weighing if you have a choice.
Advisories point at the next bill rather than this one: brakes was flagged on 31.2% of tests without failing them.
The trend is improving — the fail rate fell from 22.1% in 2021 to 20.5% in 2025, as the worst-kept examples leave the fleet.
How it compares
By model year
Every 320 model year with a usable sample. Years with their own detailed report are linked.
| Year | Tests | Pass rate | Fail rate | Most common failure |
|---|---|---|---|---|
| 1992 | 59 | 91.5% | 8.5% | Tyres |
| 1993 | 777 | 83.1% | 16.9% | Lighting & signalling |
| 1994 | 89 | 87.6% | 12.4% | Lighting & signalling |
| 1995 | 72 | 88.9% | 11.1% | Emissions & environmental |
| 1998 | 42 | 73.8% | 26.2% | Lighting & signalling |
| 1999 | 55 | 81.8% | 18.2% | Brakes |
| 2000 | 123 | 77.2% | 22.8% | Lighting & signalling |
| 2001 | 92 | 78.3% | 21.7% | Lighting & signalling |
| 2002 | 59 | 78.0% | 22.0% | Suspension |
| 2003 | 96 | 76.0% | 24.0% | Suspension |
| 2004 | 140 | 71.4% | 28.6% | Brakes |
| 2005 | 220 | 75.4% | 24.6% | Suspension |
| 2006 | 445 | 77.1% | 22.9% | Suspension |
| 2007 | 552 | 77.5% | 22.5% | Brakes |
| 2008 | 375 | 77.9% | 22.1% | Suspension |
| 2009 | 258 | 72.5% | 27.5% | Suspension |
Most common failures (all years)
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 10.0% | 355 |
| 2 | Suspension | 9.3% | 332 |
| 3 | Brakes | 7.5% | 266 |
| 4 | Tyres | 4.2% | 149 |
| 5 | Emissions & environmental | 4.0% | 143 |
| 6 | Visibility | 3.1% | 109 |
| 7 | Body, structure & corrosion | 2.9% | 102 |
| 8 | Steering | 2.3% | 83 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Headlamp aim | 169 |
| 2 | Ball joint | 167 |
| 3 | Rigid brake pipes | 122 |
| 4 | Coil spring | 101 |
| 5 | Catalyst emissions | 95 |
| 6 | Tread depth | 90 |
| 7 | Position lamp | 87 |
| 8 | Headlamp | 82 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Brakes | 31.2% | 1,109 |
| 2 | Suspension | 23.5% | 836 |
| 3 | Tyres | 21.9% | 778 |
| 4 | Emissions & environmental | 16.8% | 595 |
| 5 | Lighting & signalling | 7.9% | 282 |
| 6 | Other defects | 7.7% | 273 |
Failure rate by mileage
Higher-mileage cars tend to fail more — often the most useful guide to real condition.
| Mileage band | Tests | Fail rate |
|---|---|---|
| 0-30k | 35 | 17.1% |
| 30-60k | 200 | 14.5% |
| 60-90k | 651 | 18.1% |
| 90-120k | 897 | 19.1% |
| 120-150k | 843 | 25.9% |
| 150k+ | 919 | 22.7% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Diesel | 1,976 | 23.4% |
| Petrol | 1,576 | 18.5% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 874 | 22.1% |
| 2022 | 802 | 20.3% |
| 2023 | 710 | 21.6% |
| 2024 | 621 | 21.4% |
| 2025 | 545 | 20.5% |
What to check before buying a Mercedes-Benz 320
- Lighting & signalling (10.0% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Suspension (9.3% of tests): Worn drop links, bushes, springs or shocks — listen for knocks over bumps and check for uneven tyre wear. Typical repair: £150–£450 per corner.
- Brakes (7.5% of tests): Pads/discs are routine wear; binding, imbalance or corroded pipes are more serious — test for pulling under braking. Typical repair: £100–£350 per axle.
Repair costs are rough UK ballpark ranges to set expectations, not quotes — actual prices vary widely by car, parts and garage.
Frequently asked questions
What is the MOT pass rate for the Mercedes-Benz 320?
78.8% of the 3,552 Mercedes-Benz 320 MOT tests in this dataset passed, a 21.2% fail rate, across model years 1992–2022.
What does the Mercedes-Benz 320 most often fail its MOT on?
Lighting & signalling, recorded in 10.0% of tests, then suspension (9.3%).
How much does mileage affect 320 MOT results?
Fail rates run at 17.1% for cars in the 0-30k band and 22.7% for 150k+, a 5.6-point difference.
Is the petrol or diesel 320 more reliable at MOT time?
On MOT-testable defects the petrol fails 18.5% of the time against 23.4% for the diesel. This covers testable items only, not engine or gearbox reliability.
Methodology & source. Based on 3,552 MOT tests. Dataset: DVSA MOT testing data (2021,2022,2023,2024,2025). Data last updated 2026-07-27. Figures reflect MOT-testable defects only — read the methodology for how these are calculated and what they don't measure.